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1
Small Ball Rebound Tester <1>#TESTER

2023.102019 Excellent Product Award of The Japan Society of Mechanical Engineers→P. 19

Small Ball Rebound Tester eNM3A10(All purpose and high quality hardness tester, portable)〜 At anytime, anywhere, for anything, the precise hardness test available 〜●Unique: The sole product in the world to test hardness(coefficient of restitution) using a small ball.
●Easy: Switch on, and just start testing! One-push operation
to prepare the next test.
●No need to cut or prepare your specimen: You candirectly test small parts*1 and large objects just as they are. *2●Minimum damage: The ball is 3 mm in diameter andweighs only 0.06 g! The left trace is very small.
●Portable: The tester weighs about 0.6 kg and is operated
by two AA batteries or USB power supply.
●Any direction: Test is possible in any direction. (upward,downward, horizontal, etc.)*1 As a guide, more than 5 mm thickness is required.
*2 It is recommended to polish the surface with #600 emery
paper. (With #100, about 2% of coefficient of restitution will
be reduced.)®

2Small Ball Rebound Tester <2>#HOW

2023.10The principle is very simple.
〜 Measure hardness by bounce (coefficient of restitution) 〜●The tester hits a sample with a small ball and measures thegoing and returning velocity. The velocity ratio is called coefficientof restitution, e.
●If deformation is 100 % elastic, the going and returning velocity
is equal and thus e = 1.
●If plastic deformation occurs, the kinetic energy of the small ballis partially lost by the work to form the indentation and therefore,
e will be less than 1.

coefficient of restitution e = V2 ／ V1
Returning velocity
V2

Going velocity
V1
Impact &deformationindentation●The more the sample is harder for plastic deformation, thelarger e will be and on the other hand, the softer the sample is,the smaller e will be.
●The theory to use a small ball as an impact body is the idea ofProf. M. Nakamura, professor emeritus of Chiba University andToyohashi University of Technology and Prof. S. Maki, professor
emeritus of Mie University. Thus, eNM is the initials of the lastnames of both professors.

Reference: Nakamura, Maki, Sasamoto: J. Mater. Test. Res., Vol.32, No.1, p.23 (1987)

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Small Ball Rebound Tester <3>2023.10#MASS

Smaller sample,
more freely – with a small balleNM

Error of coefficient ofrestitution (%)
反発係数の変化(%)

〜 You can test the smaller sample easily and correctly 〜eNM

On steel anvil(center and edge)

On wooden anvil(center)

On wooden anvil(edge)●The mass (0.06 g) of the small ball of eNM tester is one
tenth to one hundreds of the impact bodies forconventional rebound hardness testers.

●The eNM tester shows the same results on the hard steel
anvil (good test condition) and on the wooden anvil (poortest condition).

●Consequently, you can test much smaller samples. *1●Furthermore, the eNM tester works even at the edge ofsample on the wooden anvil without problems.

*1 As a guide, more than 5 mm of thickness is required.

Reference: T. Yamamoto et al.: J. Mater. Test. Res., Vol. 58, No. 2, p. 75 (2013)

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Small Ball Rebound Tester <4>#ITEM

2023.10You can test various materials
Coefficient of restitution of various materials (reference value)Iteme

40 HV Pure copper hardness standard block ( ∅64 x 10 mm, 265 g)
Boiled egg, shelled (60 g)
Natural rubber block (50 mm thick)
100 HV brass hardness standard block ( ∅64 x 10 mm, 255 g)
Wooden bat for juniors (made in 1962, 800 mm long, 560 g)
200 HV steel hardness standard block ( ∅64 x 15 mm, 380 g)
Polyethylene cooking board (13 mm thick)
Dried bonito (Katsuobushi) (250 g)
400 HV steel hardness standard block ( ∅64 x 15 mm, 380 g)
Granite plate (10 mm thick, 2.3 kg)
800 HV steel hardness standard block ( ∅64 x 15 mm, 380 g)
Crystal glass ashtray (1.9 kg)

0.19
0.26
0.38
0.44
0.48
0.55
0.63
0.70
0.72
0.87
0.90
0.98

〜 Testing a Katsuobushi (dried bonito) 〜●You can test on a flat and smooth surface from which the small ball reflects and returns straight.
●As a guide, the sample requires more than 5 mm thickness.
●A demonstration tester is available. If you like to test your sample, please contact with our agencies.
Reference: T. Yamamoto et al.: J. Mater. Test. Res., Vol. 59, No. 3, p. 148 (2014)
R. Sato and Y. Nakai: J. Mater. Test. Res., Vol. 62, No. 2, p. 89 (2017)

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Small Ball Rebound Tester <5>#PARTS

2023.10

Practical parts, directly

Steel nut (M12)

Steel cylinder (55mm dia.)

Aluminum wheel for automobile

You can test various shaped practical parts, from small to big, such as nuts, cylinders, aluminum
wheels, that are difficult to test with conventional rebound hardness testers.
Reference: T. Yamamoto: J. Mater. Test. Res., Vol. 66, No. 1, p. 32 (2021)

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Small Ball Rebound Tester <6>#ICE2023.10

Testing the hardness of popsicle “Azuki bar”
(YouTube video)〜 Hardness tester that can test ice 〜●We tested the popsicle “Azuki bar” by IMURAYAGROUP Co., Ltd., well-known for its high hardness.
●As shown on the photograph, Azuki bar was cooled by
dry ice to -25℃ and then tested. (Warning: please
note that this kind of test at such low temperature may
be out of the warranty of your tester.)●The hardness (coefficient of restitution) is about 0.34
and is harder than ship biscuit (about 0.26) at theroom temperature.

eNM tester

Azuki bar

●Please watch the video (about 1 minute) from thefollowing link. (in Japanese)

dry ice

Link https://www.youtube.com/watch?v=3k3iZkVLdRw

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Small Ball Rebound Tester <7>#WORK

2023.10Hardness change before and after bending(YouTube video)〜 Test work hardening by your hand, on a desk 〜

eNM tester●Generally speaking, if you deform metallic material, it
hardens (work hardening). This experiment compared thehardness (coefficient of restitution) of brass plate beforeand after bending.
●The hardness (coefficient of restitution) is 0.30 beforebending and 0.42 after bending. It clearly shows hardness
increase by work hardening.
●Please watch the uncut video showing the wholeexperiment, hardness test – bending – retest in just 2
minutes and 20 seconds. (in Japanese)

Link https://www.youtube.com/watch?v=TYS_pBoxlls

brass plate(after bending)Translation: What will be the rebound hardness(coefficient of restitution) after bending …...

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Small Ball Rebound Tester <8>#ROBOT

2023.10

Automatic hardness testing (YouTube video)● Our eNM tester can be combined with a robot for automatic hardness testing. The followings
are two examples.
eNM tester

https://youtu.be/N5NihuaXjK4(No.1)【The First System】【Basic Operation】
Duration 50s

https://youtu.be/5imiO5JDTOU(No. 2)【Hi-Speed】【Vickers Hardness Conversion】
Duration 90s●Automatic hardness testing system, which has the eNM tester fixed to a robot hand, can obtainhardness distribution of specimens by changing testing positions.
●Automation is easy since the operation of the eNM tester, i.e., shooting and reloading, issimple and straightforward.

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9Small Ball Rebound Tester <9>#TABLET

2023.10Hardness testing of drug tablets
・Commercially available mint tablets were used as drugtablet models and were tested by 2-mm-alumina-ballrebound hardness tester under different humidity conditions.
MINTIA BREEZE
mass ca. 0.76g, diameter ca. 11mm, thickness ca. 7.2mm
e
2 weeks in the dry cabinet (25% humidity)
0.615
2 weeks by the room window (50% humidity)
0.518

・The mint tablet kept for two weeks in the dry cabinet (25%Mint tablet(ca. 11 mm diameter)
Mint tablethumidity) is clearly harder than that placed by the room
window (50% humidity). The small ball rebound hardness
tester can easily and quantitatively detect hardness
difference under various conditions.
Testing (horizontally)®

10Small Ball Rebound Tester <10>

#LONGTERM 2023.10

Monitoring hardness over long term
〜 detect change of material by its hardness 〜
Coefficientof restitution
反発係数0.550●The plastic cray (vinyl acetate emulsion) of about 8 mm
thick that is available at a dollar shop has been kept ina room for about 2 months and the coefficient ofrestitution has been measured.
●As shown in the chart, you can evaluate its hardening
process easily and quantitatively.
●By monitoring hardness, you can diagnose material
degradation.

Plastic craymm 厚thick)
樹脂粘土
約 (88mm

0.500
0.450
0.400
0.350
0.300
0.250
0.200

10100

1000

Time (h) (h)
経過時間Time dependence of hardness(coefficient of restitution)

10000

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Small Ball Rebound Tester <11>

#BAR

2023.10Figuring out the cause of the broken pinch bar– one day, at working site
●One day the pinch bar tip was suddenly
broken at working site.
●Small pieces of the broken pinch bar werecollected and tested by eNM tester. It was
found that the hardness (coefficient ofrestitution) was 0.78, which was harder thanordinary material of 0.65. It is presumed thatthe material was not properly treated bytempering after quenching.
broken pinch bar●Our eNM tester helps you test the small
materials at working site when needed, whichis quite efficient for manufacturing.

eNM tester(prototype)

Cooperated by: Kakihara Company, Funabashi City, Chiba Prefecture, Japan®

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Small Ball Rebound Tester <12>#STAND

2023.10

Combination with a universal stand〜 The surface of complicated parts can be easily tested. 〜levereNM testersample

1. Set eNM tester and sample in position

2. Push the lever down and test sample®

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Small Ball Rebound Tester <13>

#CUSTOM

Customizing parts available
for various needs

2023.10

New!

“Mount-type display”“Adapter for narrow space”“Targeting scope”

These are in the stage of development and if you
are interested in customizing, please contact ourdevelopment team through our agencies.

“Adapter for curved surface”

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Small Ball Rebound Tester <14>

#CONV

2023.10

Conversion table between coefficient of restitution
and other hardness〜 A guide to compare the coefficient of restitution e with other hardness 〜●In general, conversion of hardness is not really precise.
Please consider it a guide.
●The conversion depends on the material. (The table shown
is for steels. Currently preparing: Al-alloy and Cu-alloy)●The conversion table may be altered without prior notice.

●You can download the full conversion table here.
Link Conversion table (in Japanese)
http://www.ystl.jp/topics/?p=1334
Link Yamamoto Scientific Tool Laboratory
http://www.ystl.jp/

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Small Ball Rebound Tester <15>#MANY

2023.10

10 times endurance test4

Coeffi cientofof restitution,restitution
Coefficiente〜 ProvedValuebothof durability
and stability 〜
coefficient of restitution

1.0
0.9
0.8

e=0.63e=0.87

0.7
0.6
0.5

0

2000

4000

6000

8000

10000

Number of test

Number of test

●To prove the durability and stability of the tester, specimen equivalent to 1000 HV was tested
for 10,000 times. For every 1,000 tests, the standard blocks of e = 0.87 and e = 0.63 were alsomeasured.
●The change of coefficient of restitution stayed within roughly 0.5 % and no particular problem
was detected for durability and stability.
●Even if the small ball in the tester is damaged, it is easy to replace it. (Not free)
Reference: T. Yamamoto and T. Obata.: J. Mater. Test. Res., Vol.. 63, No. 2, p. 95 (2018)

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Small Ball Rebound Tester <16>

#TEMP

2023.10Hardness test at high and low temperature〜 Possibility of hardness at various temperature 〜●As the small ball touches the sample only for an instant, it isconsidered to be suitable for hardness test at high or low temperature.
●The right chart shows the dependence of coefficient of restitution ofSK85 carbon tool steel on temperature from -196 to +1000 ℃, tested
by eNM tester (prototype).
●At present, the development is progressing, and if you are interested,
please contact our agencies or distributors.

Coefficient of restitution, e(in the stage of development)

Temperature (℃)
Reference: T. Yamamoto et al.: proc. 84th symposium of Japan Society for Heat Treatment, p.65 (2017)

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Small Ball Rebound Tester <17>#LINEUP

2023.10

Future lineup of eNM-series testers〜 Testers with suitable ball size to be available 〜
5 mm

3 mm (current product)
2 mm

←1 mm

●Currently, eNM testers with ball size of 3 mm (product), and 1 mm, 2 mm, and 5 mm (all prototypes) has
been manufactured.
●The smaller the ball, the smaller and thinner sample can be tested. Please refer to the next page.
●With the larger ball, test is less affected by surface roughness or unevenness.
●Coefficient of restitution dose not change with different ball sizes in principle. (Similarity law of hardness)®

18Small Ball Rebound Tester <18>

#SIZE

2023.10Ball size and coefficient of restitution〜 Tester with a smaller ball is suitable for thinner sample 〜
Coefficient of restitution, e

0.9
0.80.7standard block (0.865)
t = 15 mm

ABS resin platet = 1.6 mm

0.6
0.5
0.4
0.3

standard block (0.630)
t = 15mm
steel platet = 3.4 mm
Test condition: on a desk mat of vinyl chloride on a conference table

1 mm

2 mm

3 mm

5 mm

Ball size●Coefficient of restitution does not change with different ball sizes in principle. (Please refer tothe solid lines of standard block data in the chart.)●If the thickness of sample is sufficient (as a guide, more than 5 mm), you can obtain the correct
coefficient of restitution with the 3 mm ball.
●To measure thinner sample correctly, you need smaller balls. (Please refer to the broken linesof thin plate data.)®

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Small Ball Rebound Tester <19>

#AWARD

Awards, applications, etc.
〜 Awards and Certificates 〜●Excellent Product Award of The Japan Society of Mechanical Engineers (2019)… Yamamoto Scientific Tool Laboratory●Certified “Monodukuri” (manufacturing) products by Chiba Prefecture (2020.2.6)… SHOUEI KOKI
●Certified “Monodukuri” Grand Prix Business by Funabashi City (2017) … SHOUEI KOKI
●Verification Certificate [JIS B 7727:2000 annex 2 Shore hardness tester] by ClassNK (2018.2.26)… Nakai Precision Machinery Mfg. Co., Ltd.
●Patent … JP No.6624564 (2019.12.6) / US 10161839 (2018.12.25) / EP 3165897 (2023.7.19)●Trademark … Registered trademark JP 6182900 (2019.9.20)~ Supported by ~●Chiba Prefecture: Subsidies for Small and Medium Business (2011-2013) and “Monodukuri”
Subsidies (2013) … Yamamoto Scientific Tool Laboratory~ Applications (updating) ~●Polishing process management ●Heat treatment management●Accident investigation●Shipping inspection●Research & Development●Deterioration diagnosis

2023.10

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Small Ball Rebound Tester <20>

#TEAM

2023.10Development Team of Small Ball Rebound Tester
Members●Koji Akatsu (FUTURE-TECH CORP.)●Tsutomu Obata (SHOUEI KOKI)●Koji Kadogawa (MCL)●Masaki Koga (Koga PE Office)●Koji Kojima (ITANI KOKI MFG.CO.,LTD.)●Tadashi Sato (IMAI TESTING MACHINE)●Ryoichi Sato (IMAI TESTING MACHINE)●Yasuo Nakai(Nakai Precision Machinery Mfg. Co., Ltd.)●Yoshiro Nakai(Nakai Precision Machinery Mfg. Co., Ltd.)●Masao Nakamura (Chiba University andToyohashi University of Technology)●Seijiro Maki (Mie University)●Tomio Minemura (FTS. , LTD)
●Kensuke Miyahara (NIMS)●Takashi Yamamoto(Yamamoto Scientific Tool Laboratory)●Masayuki Yamamoto(Yamamoto Scientific Tool Laboratory)(in Japanese syllabary order)®

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Small Ball Rebound Tester <21>Contact#SHOP

2023.10

Sales Agencies (Development Team Members)●IMAI TESTING MACHINE

http://www.imaitester.com/●Nakai Precision Machinery Mfg. Co., Ltd.

http://www.nakaiseiki.co.jp/●SHOUEI KOKI

http://syoueikouki.co.jp/●FTS. , LTD

http://www.fts-web.jp/●FUTURE-TECH CORP.

http://www.ft-hardness.com/

Distributors●SANSHO KENMAZAI CO.,LTD.

http://www.3sho.co.jp/other/enm3a10●SHIMADZU SCIENCE EAST CORPORATION. https://www.sse-shimadzu.co.jp/

Latest version of this PDF(Japanese version)(Video in Japanese)

http://www.ystl.jp/eNM-E.pdf

http://www.ystl.jp/eNM.pdf

http://www.ystl.jp/eNM.mp4